U.S. patent application number 14/424605 was filed with the patent office on 2015-07-30 for electric storage device and method for producing the same.
This patent application is currently assigned to SHOWA DENKO K.K.. The applicant listed for this patent is SHOWA DENKO K.K.. Invention is credited to Masatoshi Kunisawa, Masahiro Ohmori, Hitoshi Yokouchi.
Application Number | 20150213967 14/424605 |
Document ID | / |
Family ID | 50182947 |
Filed Date | 2015-07-30 |
United States Patent
Application |
20150213967 |
Kind Code |
A1 |
Yokouchi; Hitoshi ; et
al. |
July 30, 2015 |
ELECTRIC STORAGE DEVICE AND METHOD FOR PRODUCING THE SAME
Abstract
An electricity storage device including at least one electrode
having one metal tab lead and plural electrode plates. The
electrode plate includes a metal foil, an undercoat layer formed on
one surface or both surfaces of the metal foil, and an active
material layer formed on a surface of the undercoat layer. The
undercoat layer includes a carbon material and the undercoat layer
has a coating weight per unit area of one surface of 0.01 to 3
g/m.sup.2. A sum total thickness of the metal foils in the
electrode plates is 0.2 to 2 mm. The electrode plates are welded to
each other in a portion where the undercoat layer is formed and no
active material layer is formed. Further, at least one of the
electrode plates is welded to the metal tab lead in a portion where
the undercoat layer is formed and no active material layer is
formed.
Inventors: |
Yokouchi; Hitoshi; (Tokyo,
JP) ; Ohmori; Masahiro; (Tokyo, JP) ;
Kunisawa; Masatoshi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHOWA DENKO K.K. |
Tokyo |
|
JP |
|
|
Assignee: |
SHOWA DENKO K.K.
Tokyo
JP
|
Family ID: |
50182947 |
Appl. No.: |
14/424605 |
Filed: |
August 29, 2013 |
PCT Filed: |
August 29, 2013 |
PCT NO: |
PCT/JP2013/005096 |
371 Date: |
February 27, 2015 |
Current U.S.
Class: |
429/211 ;
29/25.03; 29/623.1; 361/502 |
Current CPC
Class: |
H01G 11/66 20130101;
H01G 11/26 20130101; H01M 10/052 20130101; H01G 11/76 20130101;
Y02E 60/10 20130101; H01G 11/28 20130101; H01M 4/587 20130101; H01M
4/661 20130101; Y02E 60/13 20130101; Y10T 29/49108 20150115; H01M
10/058 20130101; Y02P 70/50 20151101; H01G 11/36 20130101; H01G
11/38 20130101; H01G 11/86 20130101; Y02T 10/70 20130101; H01M
4/366 20130101; H01M 10/0525 20130101; H01G 11/72 20130101; H01M
2/266 20130101; H01M 4/667 20130101; H01G 11/04 20130101; H01M
4/133 20130101; H01M 4/663 20130101 |
International
Class: |
H01G 11/36 20060101
H01G011/36; H01M 10/058 20060101 H01M010/058; H01G 11/26 20060101
H01G011/26; H01M 4/36 20060101 H01M004/36; H01M 4/133 20060101
H01M004/133; H01M 10/0525 20060101 H01M010/0525; H01M 4/587
20060101 H01M004/587; H01G 11/86 20060101 H01G011/86; H01G 11/04
20060101 H01G011/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 29, 2012 |
JP |
2012-188605 |
Claims
1-14. (canceled)
15. An electricity storage device comprising at least one electrode
comprising a metal tab lead and at least two electrode plates, in
which the electrode plate comprises a metal foil, an undercoat
layer formed on one surface or both surfaces of the metal foil, and
an active material layer formed on a surface in a part of a portion
where the undercoat layer is formed, the undercoat layer comprises
a carbon material and the under coat layer has a coating weight per
unit area of one surface of 0.05 to 3 g/m.sup.2, the electrode
plates are welded to each other in a portion where the undercoat
layer is formed and no active material layer is formed, at least
one of the electrode plates is welded to the metal tab lead in a
portion where the undercoat layer is formed and no active material
layer is formed.
16. The electricity storage device according to claim 15, wherein a
sum total thickness of the metal foils in the electrode plates is
0.2 to 2 mm.
17. The electricity storage device according to claim 15, wherein
the undercoat layer comprises 1 to 60% by mass of the carbon
material.
18. The electricity storage device according to claim 15, wherein
the undercoat layer comprises 20 to 300 parts by mass of a binding
agent based on 100 parts by mass of the carbon material.
19. The electricity storage device according to claim 18, wherein
the biding agent is chitosan or a derivative thereof.
20. The electricity storage device according to claim 15, wherein
an area of the active material layer is 80 to 99% by area of an
area of the portion where the undercoat layer is formed.
21. The electricity storage device according to claim 15, wherein
the metal tab lead comprises at least one selected from the group
consisting of aluminum, copper, and nickel.
22. The electricity storage device according to claim 15, wherein
the metal foil is an aluminum foil or a copper foil.
23. The electricity storage device according to claim 15, wherein
the each metal foil has a thickness of 5 to 70 .mu.m.
24. The electricity storage device according to claim 15, wherein
the carbon material comprises at least one selected from the group
consisting of graphite, conductive carbon black, carbon nanotube,
and carbon nanofiber.
25. The electricity storage device according to claim 15 is a
lithium-ion battery.
26. A method for producing the electricity storage device according
to claim 15, the method comprising the steps of: preparing the
electrode plates, in which the electrode plate comprises the metal
foil, the undercoat layer formed on one surface or both surfaces of
the metal foil, and the active material layer formed on the surface
in a part of the portion where the undercoat layer is formed; and
welding the electrode plates to each other in the portion where the
undercoat layer is formed and no active material layer is formed
and welding at least one of the electrode plates to the metal tab
lead in the portion where the undercoat layer is formed and no
active material layer is formed.
27. The production method according to claim 26, wherein the
welding steps are performed by one shot welding.
28. The production method according to claim 26, wherein the
welding steps are performed by ultrasonic welding.
Description
TECHNICAL FIELD
[0001] The present invention relates to an electricity storage
device and a method for producing the electricity storage device.
More specifically, the present invention relates to an electricity
storage device comprising an electrode configured by welding one
metal tab lead and at least two electrode plates, and a method for
producing the electricity storage device.
BACKGROUND ART
[0002] As an electricity storage device, there are known a
secondary battery such as a nickel hydrogen battery, a
nickel-cadmium battery, a lead storage battery, a lithium-ion
secondary battery and the like and a capacitor such as an electric
double layer capacitor, a lithium-ion capacitor, and the like. Of
these, the lithium-ion secondary battery is used for an electric
vehicle, a hybrid car, and the like. Further, the electric double
layer capacitor is used as a back-up power supply in instantaneous
power failure and the like.
[0003] The lithium-ion secondary battery comprises at least a
positive electrode plate and a negative electrode plate. The
positive electrode plate is configured by forming a positive
electrode active material layer on a current collector such as an
aluminum foil and the like. In the positive electrode active
material layer, a transition metal oxide containing lithium, or the
like is used as a positive electrode active material. The negative
electrode plate is configured by forming a negative electrode
active material layer on a negative electrode current collector
such as a copper foil and the like. In the negative electrode
active material layer, a carbon material such as graphite is used
as a negative electrode active material. As a terminal for taking
out current from the positive electrode plate or the negative
electrode plate, a metal tab lead is used, in which the metal tab
lead is welded to each of the positive electrode plate and the
negative electrode plate. The welding of the metal tab lead is
carried out in a portion where the current collector is
exposed.
[0004] The electric double layer capacitor comprises at least a
pair of electrode plates. The electrode plate is configured by
forming an active material layer on a current collector such as an
aluminum foil and the like. In the active material layer, a carbon
material such as activated carbon and the like having large
specific surface area is used as an active material. As terminal
for taking out current from the electrode plates, a metal tab lead
is employed in which the metal tab lead is welded to each of the
electrode plates. The welding of the metal tab lead is carried out
in a portion where the current collector is exposed.
[0005] In the electricity storage device, high capacity and high
speed charging and discharging are being demanded to respond to
applications such as an electric vehicle, electrically-powered
equipment, and the like. As one measure for responding to this
demand, it has been proposed that an undercoat layer is disposed
between an active material layer and a current collector to reduce
a resistance of a contact interface between the active material
layer and the current collector (for example, Patent Documents 1 to
4). Also in an electrode plate provided with an undercoat layer, a
metal tab lead is welded in a portion where a current collector is
exposed, i.e., in a portion where neither the undercoat layer nor
an active material layer is formed (for example, Patent Document
1).
PRIOR ART LITERATURES
Patent Documents
[0006] Patent Document 1: JP 2010-170965 A (US 2011/274971 A1)
[0007] Patent Document 2: JP 2001-351612 A [0008] Patent Document
3: JP 2008-098590 A [0009] Patent Document 4: JP 2012-073396 A (US
2012/078629 A1)
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0010] As a method for forming an exposed portion of a current
collector, there is known a method for forming neither an undercoat
layer nor an active material layer in a portion to be welded on a
current collector. When the portion to be welded is previously
provided, the versatility of the current collector is decreased,
resulting in inconvenience in production of a wide variety of
electrodes. As another method, a method for partially removing an
undercoat layer and an active material layer formed on a current
collector is known. In this case, a step of removing the undercoat
layer and the active material layer is added, resulting in a
decrease in productivity.
[0011] In order to produce a high-capacity battery, at least two
positive electrode plates and at least two negative electrode
plates are occasionally stacked respectively. Also, in the electric
double layer capacitor, in order to increase capacitance, plural
electrode plates are occasionally stacked. When a plurality of
electrode plates are used, the above-described problem in forming a
current collector-exposed portion becomes serious.
[0012] An object of the present invention is to provide a method
for producing, with high productivity, an electricity storage
device comprising an electrode configured by welding one metal tab
lead and at least two electrode plates.
Means for Solving the Problems
[0013] Extensive studies by the present inventors for achieving the
object result in finding an electricity storage device and a method
for producing the electricity storage device including the
following aspects.
[0014] The present invention includes the following aspects. [0015]
(1) An electricity storage device comprising at least one electrode
comprising a metal tab lead and at least two electrode plates,
wherein
[0016] the electrode plate comprises a metal foil, an undercoat
layer formed on one surface or both surfaces of the metal foil, and
an active material layer formed on a surface in a part of a portion
where the undercoat layer is formed;
[0017] the undercoat layer comprises a carbon material and the
undercoat layer has a coating weight per unit area of one surface
of 0.05 to 3 g/m.sup.2;
[0018] the electrode plates are welded to each other in a portion
where the undercoat layer is formed and no active material layer is
formed; and
[0019] at least one of the electrode plates is welded to the metal
tab lead in a portion where the undercoat layer is formed and no
active material layer is formed. [0020] (2) The electricity storage
device according to (1), wherein a sum total thickness of the metal
foils in the electrode plates is 0.2 to 2 mm. [0021] (3) The
electricity storage device according to (1) or (2), wherein the
undercoat layer comprises 1 to 60% by mass of the carbon material.
[0022] (4) The electricity storage device according to any one of
(1) to (3), wherein the undercoat layer comprises 20 to 300 parts
by mass of a binding agent based on 100 parts by mass of the carbon
material. [0023] (5) The electricity storage device according to
(4), wherein the biding agent is chitosan or a derivative thereof.
[0024] (6) The electricity storage device according to any one of
(1) to (5), wherein an area of the active material layer is 80 to
99% by area of an area of the portion where the undercoat layer is
formed. [0025] (7) The electricity storage device according to any
one of (1) to (6), wherein the metal tab lead comprises at least
one selected from the group consisting of aluminum, copper, and
nickel. [0026] (8) The electricity storage device according to any
one of (1) to (7), wherein the metal foil is an aluminum foil or a
copper foil. [0027] (9) The electricity storage device according to
any one of (1) to (8), wherein the each metal foil has a thickness
of 5 to 70 .mu.m. [0028] (10) The electricity storage device
according to any one of (1) to (9), wherein the carbon material
comprises at least one selected from the group consisting of
graphite, conductive carbon black, carbon nanotube, and carbon
nanofiber. [0029] (11) The electricity storage device according to
any one of (1) to (10) is a lithium-ion battery. [0030] (12) A
method for producing the electricity storage device according to
any one of (1) to (11), the method comprising the steps of:
[0031] preparing the electrode plates, in which the electrode plate
comprises the metal foil, the undercoat layer formed on one surface
or both surfaces of the metal foil, and the active material layer
formed on the surface in a part of the portion where the undercoat
layer is formed; and
[0032] welding the electrode plates to each other in the portion
where the undercoat layer is formed and no active material layer is
formed and
[0033] welding at least one of the electrode plates to the metal
tab lead in the portion where the undercoat layer is formed and no
active material layer is formed. [0034] (13) The production method
according to (12), wherein the welding steps are performed by one
shot welding. [0035] (14) The production method according to (12)
or (13), wherein the welding steps are performed by ultrasonic
welding.
Advantageous Effects of the Invention
[0036] The production method according to the present invention
makes it possible to obtain, with high productivity, an electricity
storage device comprising an electrode configured by welding one
metal tab lead and at least two electrode plates using a simple
method. The electricity storage device according to the present
invention has large capacitance, small internal resistance, and
favorable cycle characteristics in rapid charge and discharge.
BRIEF DESCRIPTION OF DRAWINGS
[0037] [FIG. 1] a view illustrating an embodiment of an electrode
plate used in the present invention.
[0038] [FIG. 2] a view illustrating a side surface when the
electrode plate is viewed from the arrow direction illustrated in
FIG. 1.
[0039] [FIG. 3] a view illustrating an embodiment of an electrode
plate used in the present invention.
[0040] [FIG. 4] a view illustrating a side surface when the
electrode plate is viewed from the arrow direction illustrated in
FIG. 3.
[0041] [FIG. 5] a view illustrating an embodiment in which
electrode plates P and electrode plates N are stacked.
[0042] [FIG. 6] a view illustrating a side surface when the
electrode plates are viewed from the arrow direction illustrated in
FIG. 5.
[0043] [FIG. 7] a view illustrating an embodiment in which
electrode plates P' and electrode plates N' are stacked.
[0044] [FIG. 8] a view illustrating a side surface when the
electrode plates are viewed from the arrow direction illustrated in
FIG. 7.
[0045] [FIG. 9] a view illustrating an embodiment in which
electrode plates P'' and electrode plates N'' are stacked.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[Electricity Storage Device]
[0046] An electricity storage device according to one embodiment of
the present invention comprises at least one electrode comprising
one metal tab lead and at least two electrode plates. Examples of
the electricity storage device comprise a lithium-ion secondary
battery, an electric double layer capacitor, and the like. Of
these, the electricity storage device according to the present
invention is suitable for the lithium-ion secondary battery. In
general, plural electrode plates located in one electrode and
plural electrode plates located in the other electrode are
alternately stacked one by one and housed in an exterior package of
an electricity storage device.
<Electrode Plate>
[0047] One electrode plate comprises a metal foil, an undercoat
layer formed on one surface or both surfaces of the metal foil, and
an active material layer formed on a surface in a part of a portion
where the undercoat layer is formed.
(Metal Foil)
[0048] The metal foil used in the present invention is a well-known
one used in a conventional electricity storage device. A material
used in the metal foil is not specifically limited, examples of the
material include a metal such as nickel, aluminum, titanium,
copper, and the like; and an alloy such as stainless steel, nickel
alloy, aluminum alloy, titanium alloy, copper alloy, and the
like.
[0049] In an electrode plate used in the positive electrode of a
lithium-ion secondary battery, as the metal foil, an aluminum foil
is preferably used, and a pure aluminum foil or an aluminum alloy
foil containing not less than 95% by mass of aluminum is more
preferably used. Examples of the pure aluminum foil include A1N30
aluminum foil and A1085 aluminum foil, and examples of the aluminum
alloy foil include A3003 (Mn-added) aluminum alloy foil.
[0050] In an electrode plate used in the negative electrode of the
lithium-ion secondary battery, as the metal foil, a copper foil or
an aluminum foil is preferably used. When graphite is used as an
active material, the metal foil is preferably a copper foil. As the
preferable copper foil, a rolled copper foil or an electrolyzed
copper foil having a purity of not less than 95% by mass is
mentioned. As the preferable aluminum foil, the same ones as those
usable for the positive electrode of the lithium-ion secondary
battery are mentioned.
[0051] In an electrode plate used in the electrode of an electric
double layer capacitor, as the metal foil, an aluminum foil is
preferably used. As the preferable aluminum foil, the same ones as
those usable for the positive electrode of the lithium-ion
secondary battery are mentioned.
[0052] From the viewpoint of easy handling of the metal foil or the
electrode plate, or size reduction of the electricity storage
device, the metal foil is preferably 5 .mu.m to 70 .mu.m, and more
preferably 5 .mu.m to 50 .mu.m in a thickness per one foil.
[0053] An area of the metal foil can be appropriately determined
depending on the application of the electricity storage device. For
example, in use as an electric vehicle power supply, the metal foil
is preferably 5000 mm.sup.2 to 1000000 mm.sup.2 and more preferably
8000 mm.sup.2 to 500000 mm.sup.2 in an area per one foil.
[0054] The metal foil may be a foil having no holes or a foil
having holes such as a two-dimensional mesh foil, a
three-dimensionally networked foil, a punching metal foil, and the
like. The metal foil may have a surface subjected to a well-known
surface treatment. Examples of the surface treatment include
roughening treatment, etching, silane coupling treatment, chromate
treatment, anodization, wash primer, corona discharge, and glow
discharge. When an electrically insulating film is formed on the
surface by the surface treatment, a thickness of the electrically
insulating film is preferably adjusted so that a function as the
current collector of the electrode plate is not decreased.
(Undercoat Layer)
[0055] The undercoat layer is formed on one surface or both
surfaces of a metal foil and preferably formed in contact with one
surface or both surfaces thereof. The undercoat layer may be formed
on a partial surface of the metal foil or on the entire surface
thereof. Formation may be made not only on a main surface of the
metal foil but also on an end face thereof. As an embodiment of
forming the undercoat layer on the partial surface of the metal
foil, there are an embodiment of forming the undercoat layer only
on a predetermined area of the metal foil surface, an embodiment of
forming the undercoat layer on the entire metal foil surface in a
patterned manner such as a dot pattern, a line-and-space pattern,
and the like.
[0056] An area of a portion where the undercoat layer is formed is
preferably not less than 95% by area of an area of the metal foil.
When the undercoat layer is formed in a patterned manner, the area
of the portion where the undercoat layer is formed is the sum of an
area of the undercoat layer literally formed and an area of the
metal foil exposed in the undercoat layer formed in the patterned
manner.
[0057] A coating weight per unit area of a surface of the undercoat
layer is 0.05 to 3 g/m.sup.2, preferably 0.1 to 2 g/m.sup.2, and
more preferably 0.1 to 0.7 g/m.sup.2. Such a coating weight per
unit area reduces an internal resistance of an electricity storage
device. Further, a welding strength between electrode plates and a
welding strength between an electrode plate and a metal tab lead
are maintained in an appropriate range.
[0058] A coating weight per unit area of the undercoat layer is a
ratio of a mass of the undercoat layer to an area of the undercoat
layer (the area is an area of the undercoat layer only, excluding
an area of the metal foil exposed in the undercoat layer formed in
a patterned manner when the undercoat layer is formed in the
patterned manner). The mass of the undercoat layer can be
calculated from a difference (W.sub.0-W.sub.1), in which, for
example, a test piece having an appropriate size is cut out from an
electrode plate and its mass W.sub.0 is measured, followed by
removing the undercoat layer from the test piece, and then a mass
W.sub.1 after removal of the undercoat layer is measured.
[0059] The coating weight per unit area can be adjusted by a
well-known method. When, for example, an undercoat layer is formed
by coating, the adjustment can be made by a solid content
concentration of a coating liquid for forming the undercoat layer
or a clearance of a coating liquid applying slit in a coater. Upon
intending to increase the coating weight per unit area, the solid
content concentration is increased or the clearance is increased.
Upon intending to decrease the coating weight per unit area, the
solid content concentration is decreased or the clearance is
decreased. Further, coating is repeatable at not less than two
times until a desired coating weight per unit area is achieved.
[0060] The undercoat layer comprises a carbon material. The carbon
material used for the undercoat layer is preferably one capable of
providing conductivity to the undercoat layer. Examples of the
carbon material include conductive carbon black such as acetylene
black, Ketjenblack, furnace black, and the like; graphite such as
artificial graphite, natural graphite, and the like; and carbon
fiber, vapor-grown carbon fiber, carbon nanotube, carbon nanofiber,
and the like. Of these, at least one selected from the group
consisting of graphite, conductive carbon black, carbon nanotube,
and carbon nanofiber is preferable, and conductive carbon black is
more preferable. These carbon materials can be used alone or in
combination of two or more.
[0061] The carbon material may be completely imbedded in the
undercoat layer or immobilized by being exposed partially from the
undercoat layer. When the undercoat layer is provided with
conductivity, the dispersion state of the carbon material in the
undercoat layer is not specifically limited. Further, it is
preferable that the carbon material does not drop off from the
undercoat layer.
[0062] A particle diameter of the carbon material is selectable so
that binding properties to another material in the undercoat layer,
the aforementioned metal foil, or an active material layer to be
described later become favorable.
[0063] An amount of the carbon material contained in the undercoat
layer is preferably 1 to 60% by mass, and more preferably 20 to 50%
by mass. When the carbon material is contained at the amount, the
conductivity of the undercoat layer is enhanced and then the
electric resistance between the metal foil and the active material
layer is reduced.
[0064] To prevent drop-off of the carbon material and to enhance
the adhesion between the metal foil and the undercoat layer or
between the active material layer and the undercoat layer, a
binding agent may be contained in the undercoat layer. An amount of
the binding agent that may be contained in the undercoat layer is
preferably 20 to 300 parts by mass, and more preferably 30 to 150
parts by mass based on 100 parts by mass of the carbon material.
Examples of the binding agent include acrylic polymers, vinyl
polymers, polyvinylidene fluoride, styrene butadiene rubbers,
polysaccharides, polysaccharide derivatives and the like. Of these,
from the viewpoint of non-aqueous electrolytic solution resistance
of the undercoat layer, polysaccharides and polysaccharide
derivatives are preferable.
[0065] Specific examples of polysaccharides include chitin,
chitosan, cellulose, and derivatives thereof. Of these, chitosan is
preferable. Examples of polysaccharide derivatives include
hydroxyalkylated polysaccharides, carboxyalkylated polysaccharides,
sulfuric esterificated polysaccharides and the like.
Hydroxyalkylated polysaccharides are preferable from the viewpoint
of large solubility to a solvent and easy formation of the
undercoat layer. Examples of a hydroxyalkyl group include a
hydroxyethyl group, a hydroxypropyl group, a glyceryl group and the
like. Of these, a glyceryl group is preferable. A hydroxyalkylated
polysaccharide can be synthesized using a well-known method. These
binding agents can be used alone or in combination of two or more.
At least two of binding agents used may be those merely mixed or
those formed with a cross-linked structure, an interpenetrating
polymer structure, or a semi-interpenetrating polymer structure. Of
these, those formed with a cross-linked structure, an
interpenetrating polymer structure, or a semi-interpenetrating
polymer structure are preferable.
[0066] The undercoat layer may comprise various types of well-known
additives as needed. As the additives, mentioned are dispersion
stabilizers, thickeners, sedimentation inhibitors, skinning
inhibitors, antifoaming agent, electrostatic coatablity improvers,
dripping inhibitors, levelling agents, cross-linking catalysts,
cissing inhibitors and the like.
[0067] When a polysaccharide or a polysaccharide derivative is
incorporated in the undercoat layer as a biding agent, an organic
acid is preferably incorporated as an additive. An added amount of
the organic acid is preferably 40 to 120 parts by mass, and more
preferably 40 to 90 parts by mass based on 100 parts by mass of the
polysaccharide or the polysaccharide derivative. As the organic
acid, carboxylic acids, sulfonic acids, phosphonic acids, and the
like are mentioned. Of these, carboxylic acids are preferable.
Examples of the carboxylic acids include
2-phosphonobutane-1,2,4-tricarboxylic acid,
1,2,3,4-butanetetracarboxylic acid, pyromellitic acid and the like.
These organic acids can be used alone or in combination of two or
more.
[0068] As a method for forming an undercoat layer on a metal foil,
gas phase method such as a sputtering method, a vapor deposition
method, a chemical vapor deposition method, and the like and
coating method such as a dipping method, a printing method, and the
like are mentioned. Of these, the coating method is preferable from
the viewpoint of being able to perform continuous processing using
a roll-to-roll system and realize cost reduction.
[0069] Formation of the undercoat layer by the coating method
comprises preparing a coating liquid comprising components
constituting the undercoat layer or precursors thereof, applying
the coating liquid on a metal foil, and drying.
[0070] Examples of a liquid medium used for the undercoat layer
coating liquid include non-protonic polar compounds such as
N-methylpyrrolidone, .gamma.-butylolactone, and the like, protonic
polar compounds such as ethanol, isopropyl alcohol, n-propyl
alcohol, and the like, and water. A solid content concentration of
the coating liquid is appropriately set so as for the undercoat
layer to have a desired coating weight per unit area.
[0071] A method for applying an undercoat layer coating liquid on a
metal foil is not specifically limited and a well-known coating
method is employable as it is. Specifically, as the method for
coating, a casting method, a bar coating method, a dipping method,
a printing method, and the like are mentioned. Of these, from the
viewpoint of easily controlling a thickness of a coated film,
preferable are bar coating, gravure coating, gravure reverse
coating, roll coating, Meyer bar coating, blade coating, knife
coating, air knife coating, Comma coating, slot diamond coat, slide
die coating, and dip coating. Upon coating on both surfaces of the
metal foil, a coating operation may be performed for one surface
each or for both surfaces at the same time.
[0072] A method for drying the coated coating liquid is not
specifically limited. Drying temperature is preferably 100 to
300.degree. C., and more preferably 120 to 250.degree. C. Drying
time is preferably 10 seconds to 10 minutes. Drying under such
conditions makes it possible to completely eliminate a liquid
medium in the undercoat layer without decomposition of components
in the undercoat layer, resulting in formation of an undercoat
layer having a favorable surface shape with high throughput.
(Active Material Layer)
[0073] An active material layer is formed on a partial surface of a
portion where an undercoat layer is formed and preferably formed in
contact with a partial surface of the portion where the undercoat
layer is formed. "A portion where an undercoat layer is formed"
comprises not only a portion of an undercoat layer literally formed
on the metal foil surface but also a portion of the metal foil
exposed in the undercoat layer formed in a patterned manner. The
active material layer is formed so that part of the portion where
the undercoat layer is formed is exposed and preferably formed so
that a marginal portion of the portion where the undercoat layer is
formed is exposed. An area of the active material layer is
preferably 80 to 99% by area, and more preferably 90 to 95% by area
of the portion where the undercoat layer is formed (the sum of an
area of the undercoat layer literally formed and an area of the
metal foil exposed in the undercoat layer formed in a patterned
manner when the undercoat layer is formed in the patterned manner).
When the active material layer is formed on both surfaces, a
portion where the undercoat layer is formed and no active material
layer is formed is preferably provided in the same position of the
both surfaces. The shape of the portion where the undercoat layer
is formed and no active material layer is formed is not
specifically limited.
[0074] With an increase in a thickness of the active material
layer, an electric capacity per electrode plate is increased, but
an internal resistance of an electricity storage device is
increased. Therefore, the thickness of the active material layer
can be appropriately set so as to realize a desired battery
capacity and the internal resistance with a predetermined value or
less. The thickness of the active material layer is preferably 10
.mu.m to 200 .mu.m.
[0075] The active material layer usually comprises an active
material and a binding agent, and a conductive assistant and an
additive as needed. As any materials, a well-known material is
employable according to the type of an electricity storage
device.
[0076] In an active material layer used for the positive electrode
of a lithium-ion secondary battery, as an active material, usable
are, for example, lithium cobalate (LiCoO.sub.2), lithiummanganate
(LiMn.sub.2O.sub.4), lithium nickelate (LiNiO.sub.2), ternary
lithium compounds (Li(Co.sub.xMn.sub.yNi.sub.z)O.sub.2) of
Co--Mn--Ni, sulfur based compound (TiS.sub.2), olivine compounds
(LiFePO.sub.4, LiMnPO.sub.4) and the like.
[0077] In an active material layer used for the negative electrode
of a lithium-ion secondary battery, as an active material, usable
are, for example, carbon materials such as artificial graphite,
natural graphite and the like; metal materials or metalloide
materials such as Sn, Si and the like; and lithium titanate and
metal oxides such as titanium oxide and the like.
[0078] Charging of the lithium-ion secondary battery proceeds in
such a manner that lithium ions having been held in a positive
electrode active material are de-intercalated and released into an
electrolytic solution, and the lithium ions in the electrolytic
solution are intercalated between crystal layers of a carbon
material that is a negative electrode active material. Further, on
the contrary of charging, discharge proceeds in such a manner that
lithium ions are released from the negative electrode active
material, and intercalated in the positive electrode active
material.
[0079] In an active material layer used for the electrode of an
electric double layer capacitor, as an active material, for
example, activated carbon is usable. As the activated carbon,
coconut shell activated carbon, fibrous active carbon, and the like
are mentioned. The activated carbon is not specifically limited by
its activation method, and those obtained by a steam activation
method, a chemical activation method, and the like are employable.
To obtain a capacitor having large capacity, those subjected to an
alkaline activation treatment, i.e., alkaline activated carbon is
preferable.
[0080] The electric double layer capacitor is not an electricity
storage system such as a lithium-ion secondary battery according to
faradaic reaction. The electric double layer capacitor is an
electricity storage system utilizing a physical phenomenon in which
cations and anions each in an electrolytic solution form an
electric double layer on the surface of the active material in the
electrode.
[0081] In an active material layer used for the electrode of the
lithium-ion secondary battery or the electric double layer
capacitor, as a conductive assistant, usable are, for example,
conductive carbon black such as acetylene black, Ketjenblack,
furnace black, and the like; graphite such as artificial graphite,
natural graphite, and the like; and carbon fiber, vapor-grown
carbon fiber, carbon nanotube, carbon nanofiber, and the like.
[0082] In the active material layer used for the electrode of the
lithium-ion secondary battery or the electric double layer
capacitor, as a binding agent, usable are, for example,
polyethylene, polypropylene, ethylene propylene copolymers,
ethylene propylene terpolymers, butadiene rubber, styrene butadiene
rubber, butyl rubber, polytetrafluoroethylene, poly(meth)acrylates,
polyvinylidene fluoride, polyethylene oxide, polypropylene oxide,
polyepichlorohydrin, polyphosphazene, polyacrylonitrile, and the
like.
[0083] A method for forming an active material layer is not
specifically limited, and a well-known method used for producing an
electricity storage device is employable. When, for example, an
active material layer is formed by a coating method, initially, an
active material is uniformly dispersed in a liquid medium, together
with a conductive assistant and a biding agent as needed, to obtain
a coating liquid. The liquid medium is not specifically limited
unless changing an undercoat layer in quality. As a liquid medium
used for an active material layer coating liquid, the same ones as
liquid medium usable for an undercoat layer coating liquid are
mentioned. As a method for applying a coating liquid and a method
for drying a coated coating liquid, a coating method and a drying
method employable upon formation of an undercoat layer are
employable as they are. After drying, press treatment is preferably
performed. The press treatment can provide an active material layer
having high density.
[0084] An electrode plate used in the present invention may
comprise another member such as a heat-resistant layer in addition
to the metal foil, the undercoat layer, and the active material
layer. The heat-resistant layer is usually provided on the active
material layer.
[0085] The electrode plate is not specifically limited by its
shape. For example, a rectangle shape as illustrated in FIG. 1 and
a notched shape as illustrated in FIG. 3 are mentioned.
<Metal Tab Lead>
[0086] A metal tab lead is not specifically limited as long as it
is used for an electricity storage device. The metal tab lead is
preferably composed of a metal foil. The metal tab lead is
preferably 0.05 to 1 mm in thickness, 5 to 150 mm in width, and 10
to 100 mm in length. A material used for the metal tab lead is not
specifically limited, examples of the material include a metal such
as nickel, aluminum, titanium, copper, and the like; and an alloy
such as stainless steel, nickel alloy, aluminum alloy, titanium
alloy, copper alloy, and the like. An aluminum foil used for the
metal tab lead is preferably one subjected to a well-known
annealing treatment. The annealing treatment is preferably
performed in inactive or reductive atmosphere. Annealing
temperature is preferably 100.degree. C. to 500.degree. C.
Annealing time varies depending on the annealing temperature, but
is preferably about 1 minute to 1 hour.
[0087] As a copper foil used for the metal tab lead, a rolled
copper foil, an electrolytic copper foil, and the like are
mentioned. Of these, a rolled oxygen-free copper foil is preferable
from the viewpoint of easiness in welding and high durability of a
welded portion. Further, as the copper foil, those subjected to
anticorrosion treatment such as chromate treatment or nickel
plating treatment are preferably used.
[0088] The metal tab lead may be composed of a laminate foil
provided with a metal coat on its metal foil surface. As the metal
coat formed on the metal foil surface, a coat mainly containing
nickel is selected. The nickel coated layer is preferably set to
have a thickness of 1 to 5 .mu.m.
[0089] An insulating film is preferably bonded to part of the
surface of the metal tab lead. As the insulating film, those formed
from an olefin-based polymer are preferable. When an electrode is
enclosed in a packaging material and sealed using a heat seal, an
insulating film bonded to the metal tab lead surface and a
packaging material sealant portion are allowed to adhere to each
other air-tightly and then insulating properties between the metal
tab lead and the packaging material can be ensured.
[Electrode]
[0090] An electrode used in the present invention comprises a metal
tab lead and at least two electrode plates. The electrode plates
constituting the electrode used in the present invention are welded
to each other in a portion where an undercoat layer is formed and
no active material layer is formed, and at least one of the
electrode plates is welded to the metal tab lead in a portion where
the undercoat layer is formed and no active material layer is
formed. A portion where an undercoat layer is formed and no active
material layer is formed (comprising not only a portion of an
exposed undercoat layer but also a metal foil exposed in the
undercoat layer formed in a pattern manner when the undercoat layer
is formed in the patterned manner) will be referred to as a tab
lead welding portion in some cases.
[0091] A plurality of electrode plates is preferably stacked so
that tab lead welding portions are disposed in the same
position.
[0092] In the plural electrode plates, it is preferable that the
electrode plates have substantially the same shape and the tab lead
welding portions have substantially the same shape. Further, in
plural electrode plates having an undercoat layer and an active
material layer formed on both surfaces of a metal foil, the pattern
shapes of the undercoat layers on the respective surfaces are
preferably substantially the same and the pattern shapes of exposed
portions of the undercoat layers on the respective surfaces are
preferably substantially the same. Such a configuration makes it
possible that when the tab lead welding portions of the electrode
plates are stacked so as to be disposed in the same position, the
edges of the electrode plates are matched and then a volume of an
electricity storage device is reduced.
[0093] A total thickness of metal foils in a plurality of electrode
plates is preferably 0.2 to 2 mm, more preferably 0.3 to 1.5 mm,
and still more preferably 0.5 to 1.5 mm. When the total thickness
of the metal foils is increased, an electricity storage device
having large capacity tends to be easily obtained. On the other
hand, when the total thickness of the metal foils is decreased, a
bending stress applied to the tab lead welding portions tends to
easily fall within an allowable range when plural electrode plates
are brought together to be welded to a metal tab lead. Plural
electrode plates are stacked, for example, by preparing preferably
10 to 100 metal foils when having a thickness of 20 .mu.m or
preferably 4 to 40 metal foils when having a thickness of 50
.mu.m.
[0094] It is preferable to alternately stack, one by one, one group
of plural electrode plates to form one electrode and the other
group of plural electrode plates to form the other electrode.
Further, a separator is preferably sandwiched between an electrode
plate for forming one electrode and an electrode plate for forming
the other electrode.
[0095] Further, with respect to an electrode plate and a metal tab
lead, a tab lead welding portion of the electrode plate is stacked
with the metal tab lead. The metal tab lead may be stacked onto a
tab lead welding portion of the outermost electrode plate of plural
electrode plates or may be stacked so as to sandwich the metal tab
lead between the tab lead welding portions of two optional
electrode plates adjacent to each other of the plural electrode
plates.
[0096] When, for example, an electrode plate has a shape as shown
in FIG. 3 and FIG. 4, a plurality of electrode plates P and a
plurality of electrode plates N are stacked as shown in FIG. 5 and
FIG. 6, and thereby, a metal tab lead 5p can be welded to a tab
lead welding portion 3p of the electrode plate P, and a metal tab
lead 5n can be welded to a tab lead welding portion 3n of the
electrode plate N. Further, a plurality of electrode plates P' and
a plurality of electrode plates N' are stacked as shown in FIG. 7
and FIG. 8, and thereby, a metal tab lead 5p' can be welded to a
tab lead welding portion 3p' of the electrode plate P', and a metal
tab lead 5n' can be welded to a tab lead welding portion 3n' of the
electrode plate N'.
[0097] As a welding method, a well-known method used for welding
metals is selected. For example, TIG welding, spot welding, laser
welding, ultrasonic welding, and the like are mentioned. Of these,
ultrasonic welding is preferable from the viewpoint of welding
strength.
[0098] Welding is performed according to the following steps. For
example, stacked electrode plates are disposed between an anvil and
a horn and a metal tab lead is disposed on tab lead welding
portions, followed being applied with ultrasonic waves, which can
realize one shot welding. The one shot welding does not refer to
one-by-one welding of plural electrode plates and a tab lead but
refers to collective welding thereof. Ultrasonic waves may be
applied by being separated into plural times as long as collective
treatment is carried out. Further, it is possible that electrode
plates are initially welded to each other and then a metal tab lead
is welded thereto. Changes in pressure, frequency, output, and
treatment time during welding make it possible to change a degree
of welding. Further, a change in the tip shape of the horn makes it
possible to change a welding area. The shape of the tip of the horn
can be, for example, needle-like, spherical and so on. Further, a
shape obtained so as to have a large number of contact points by
providing irregularities as seen in an embossing die is employable
for the tip of the horn. The welding area refers to an area of a
portion applied with ultrasonic waves by being brought into contact
with a metal tab lead. The welding area can be appropriately set
according to a shape and area of a tab lead welding portion. For
example, the welding area can be set to be preferably 1 to 50%, and
more preferably 2 to 40% of an area of one surface of the tab lead
welding portion.
[0099] The electricity storage device according to the present
invention can employ an electrode having a structure as described
above as a positive electrode and a negative electrode or as any
one of the positive electrode and the negative electrode. Further,
the electricity storage device according to the present invention
can employ an electrode having a structure as described above as
one electrode and a well-known electrode as the other
electrode.
(Separator)
[0100] To prevent short circuit, a separator S is disposed between
a positive electrode plate and a negative electrode plate. As the
separator, those formed of a porous insulating material such as
non-woven cloth, woven cloth, porous film, and the like. Examples
of the porous film include microporous film made of polyethylene or
polypropylene. Further, the separator may comprise a heat-resistant
layer comprising inorganic oxide particles.
[0101] A positive electrode and a negative electrode in which a
separator is sandwiched therebetween as described above are housed
in a packaging material such as a metal can, a laminated bag, and
the like. Then, an electrolyte is placed therein and the
electrolyte is impregnated into the positive electrode and the
negative electrode with elimination of moisture. Lastly, the
packaging material is vacuum-sealed and thereby, an electricity
storage device can be obtained. When as the electrolyte, a gel or
solid electrolyte is used, a separator may be omitted.
(Electrolyte)
[0102] As an electrolyte, employable are well-known materials used
for an electricity storage device such as a lithium-ion secondary
battery, an electric double layer capacitor, and the like.
[0103] As the electrolyte used for the lithium-ion secondary
battery, for example, a non-aqueous electrolytic solution, a
polymer electrolyte, an inorganic solid electrolyte, a molten salt
electrolyte, and the like can be mentioned.
[0104] The non-aqueous electrolytic solution is a solution obtained
by dissolving an electrolyte salt in a non-aqueous organic solvent.
As the electrolyte salt, fluorine-containing lithium salts such as
lithium hexafluorophosphate (LiPF.sub.6), lithium tetrafluoroborate
(LiBF.sub.4), and the like can be mentioned. As the non-aqueous
organic solvent, ethylene carbonate (EC), dimethyl carbonate (DMC),
and the like can be mentioned.
[0105] As the polymer electrolyte, those obtained by incorporating
the aforementioned electrolyte salt into a polymer containing a
polyethylene oxide derivative and a derivative thereof, a polymer
containing a polypropylene oxide derivative and a derivative
thereof, a phosphate polymer, a polymer containing a polycarbonate
derivative and a derivative thereof, or the like can be
mentioned.
[0106] As the inorganic solid electrolyte, those containing sulfide
glass as a main component are mentioned. Glass ceramics in which,
for example, lithium sulfide and at least one selected from the
group consisting of silicon sulfide, germanium sulfide, phosphorous
sulfide and boron sulfide are combined can be used. Of these, glass
ceramics in which lithium sulfide and phosphorous sulfide are
combined is preferably used due to large ionic conductivity.
[0107] Examples of the molten salt electrolyte include those
obtained by combining methylpropylimidazolium
bis(fluorosulfonyl)amide and lithium
bis(trifluoromethane)sulfonamide.
[0108] Examples of the electrolyte used for the electric double
layer capacitor include a water-soluble electrolytic solution and a
non-aqueous electrolytic solution. As the water-soluble
electrolytic solution, a sulfuric acid aqueous solution, a sodium
sulfate aqueous solution, a sodium hydoxide aqueous solution, and
the like are mentioned. Further, the non-aqueous electrolytic
solution refers to a solution obtained by dissolving a cationic
electrolyte or an anionic electrolyte in a non-aqueous solvent. As
the cationic electrolyte, a tetraethylammonium salt and the like
are mentioned. As the anionic electrolyte, tetrafluoroborate ion
(BF.sub.4.sup.-), bis(trifluoromethylsulfonyl)imide
((CF.sub.3SO.sub.2).sub.2N.sup.-), and the like are mentioned. As
the non-aqueous solvent, ethylene carbonate (EC), dimethyl
carbonate (DMC), and the like are mentioned.
(Packaging Material)
[0109] As a packaging material, a well-known packaging material
used for an electricity storage device is selectable, and a
laminated packaging material is preferable. A configuration of the
laminated packaging material is not specifically limited, and those
having a polymer layer on both sides of an aluminum foil are
mentioned. For a polymer layer serving as the exterior of the
electricity storage device, for example, a polyamide, those
obtained by laminating a polyester on a polyamide, and the like are
used from the viewpoint of heat resistance, sticking strength,
lubricating properties, printability, and others. As a polymer
layer of the interior, a thermoplastic polyolefin and the like
serving as a heat sealant are used.
EXAMPLES
[0110] More specifically, the present invention will be described
with reference to examples and comparative examples. The scope of
the present invention is not limited by the present examples.
Appropriate modifications can be made without modifying the gist of
the present invention to carry out the present invention.
Example 1
<Preparation of Undercoat Layer Coating Liquid>
[0111] There were mixed 10 parts by mass of acetylene black (trade
name: DENKA BLACK (HS-100), produced by Denki Kagaku Kogyo K.K.), 5
parts by mass of dihydroxypropylchitosan (deacetylation degree: 86
mol %, weight average molecular weight: 9.0.times.10.sup.4), 5
parts by mass of pyromellitic dianhydride, and
N-Methyl-2-pyrrolidone (industrial grade), followed by being mixed
therewith using a dissolver type stirrer at a rotation rate of 300
rpm for 10 minutes. Subsequently, using a homogenizer (product
name: PRO200, produced by Ieda Trading Corp.), homogenization was
carried out at 20000 rpm for 30 seconds to obtain an undercoat
layer coating liquid having a solid content concentration of 7% by
mass.
<Formation of Undercoat Layer>
[0112] The undercoat layer coating liquid was applied entirely on
one surface of an aluminum foil (A1N30 material) having a thickness
of 20 .mu.m using a bar coating method. Thereafter, heat treatment
was carried out for 3 minutes at 180.degree. C. for drying. Then,
on the other surface, the undercoat layer coating liquid was
applied in the same manner to obtain an aluminum foil having an
undercoat layer formed on the both surfaces (hereinafter,
occasionally referred to as an Al current collection member). A
coating weight per unit area of one surface of the undercoat layer
was 0.5 g/m.sup.2. In measurement of the coating weight per unit
area of one surface, a small thin piece having a size of 100
mm.times.100 mm was accurately cut out from the Al current
collection member and one surface of the small thin piece was
treated with a remover (trade name: NEOREVER#346, produced by
Sansai Kako Co., Ltd.) and the undercoat layer was removed from the
one surface of the small thin piece for calculation based on a mass
difference before and after the removal.
<Production of Positive Electrode Plate>
[0113] A small thin piece (hereinafter, occasionally referred to as
an Al current collector) having a size of 100 mm.times.100 mm was
cut out from the Al current collection member.
[0114] There were mixed 95 parts by mass of lithium cobalate (trade
name: CELLSEED C, produced by Nippon Chemical Industries Co.,
Ltd.), 2 parts by mass of acetylene black (trade name: DENKA BLACK
(powdery article), produced by Denki Kagaku Kogyo K.K.), 3 parts by
mass of polyvinylidene fluoride (trade name: KF POLYMER#1120,
produced by Kureha Corp.), and 95 parts by mass of
N-methyl-2-pyrrolidone (industrial grade) to obtain a slurry.
[0115] The slurry was applied on both surfaces of the Al current
collector using a doctor blade method with the exception of a
marginal portion of 100 mm long.times.10 mm wide on one side edge
of the Al current collector. Thereafter, drying was carried out,
followed by pressing to form a positive electrode active material
layer of 90 mm wide.times.100 mm long.times.50 .mu.m thick on each
of the both surfaces of the Al current collector. The resulting
product was used as a positive electrode plate P''. The marginal
portion of 10 mm wide.times.100 mm long where the undercoat layer
was exposed and no positive electrode active material layer was
formed was used as a tab lead welding portion 3P''.
<Production of Negative Electrode Plate>
[0116] There were mixed 94 parts by mass of artificial graphite
(trade name: SCMG-AR, produced by Showa Denko K.K.), 1 part by mass
of acetylene black (trade name: DENKA BLACK (powdery article),
produced by Denki Kagaku Kogyo K.K.), 5 parts by mass of
polyvinylidene fluoride (trade name: KF POLYMER#9130, produced by
Kureha Corp.), and 94 parts by mass of N-methyl-2-pyrrolidone
(industrial grade) to obtain a slurry.
[0117] An electrolyte copper foil of 100 mm wide.times.100 mm
long.times.10 .mu.m thick was prepared.
[0118] The slurry was applied on both surfaces of the electrolyte
copper foil using a doctor blade method with the exception of a
marginal portion of 10 mm wide.times.100 mm long on one side of the
electrolyte copper foil. Thereafter, drying was carried out,
followed by pressing to form a negative electrode active material
layer of 90 mm wide.times.100 mm long.times.55 .mu.m thick on each
of the both surfaces of the electrolyte copper foil. The resulting
product was used as a negative electrode plate N''. The marginal
portion of 10 mm wide.times.100 mm long where the copper foil was
exposed and no negative electrode active material layer was formed
was used as a tab lead welding portion 3n''.
[0119] As shown in FIG. 9, 15 positive electrode plates and 16
negative electrode plates were alternately stacked one by one so
that the tab lead welding portions 3p'' and 3n'' were pulled out in
opposite directions, and a separator (trade name: Celgard 2500,
produced by Polypore International, Inc.) was inserted between the
positive electrode plate and the negative electrode plate to obtain
an electrode plate laminate in which the outermost layers of the
laminate were the negative electrode plate, respectively.
[0120] Then, a positive electrode tab lead (made of A1N30-H
(aluminum), a size of 0.5 mm thick.times.20 mm wide.times.30 mm
long) 5P'' was prepared. One positive electrode tab lead 5P'' and
15 tab lead welding portions 3p'' of the positive electrode plates
in the electrode plate laminate were welded using an ultrasonic
welder. The welding was carried out under conditions involving a
horn tip angle of 90 degrees, a pressure of 0.3 MPa, a frequency of
20 kHz, and a duration of 0.3 seconds. The tip of the horn had a
rectangular shape of 2 mm.times.12 mm, and welding area was 24
mm.sup.2.
[0121] A negative electrode tab lead (made of oxygen-free copper, a
size of 0.2 mm thick.times.20 mm wide.times.30 mm long, coated
nickel: 1 .mu.m) 5n'' was prepared. One negative electrode tab lead
5n'' and 16 tab lead welding portions 3n'' of the positive
electrode plates in the electrode plate laminate were welded using
an ultrasonic welder. The welding was carried out under conditions
involving a horn tip angle of 90 degrees, a pressure of 0.3 MPa, a
frequency of 20 kHz, and a duration of 0.3 seconds. The tip of the
horn had a rectangular shape of 2 mm.times.12 mm, and welding area
was 24 mm.sup.2.
[0122] The electrode plate laminate was covered with an aluminum
laminated packaging material with the positive electrode tab and
the negative electrode tab each protruded, and three sides were
sealed to form a bag-like shape having one side open. Water was
eliminated using a vacuum dryer set at 60.degree. C. Thereafter, as
an organic electrolytic solution, a LiPF.sub.6 solution (produced
by Kishida Chemical Co., Ltd.) was poured in, followed by
impregnation for 24 hours in vacuum atmosphere. The opening of the
aluminum laminated packaging material was sealed using a vacuum
sealer to produce a lithium-ion secondary battery for evaluation
tests.
<Evaluation Tests of Lithium-Ion Secondary Battery>
(Measurement of Tab Lead Welding Strength)
[0123] The measurement was carried out using a tabletop material
testing machine (STA-1150, produced by Orientech Co., Ltd.) in a
tensile test mode. The positive electrode tab lead and the battery
body part of the lithium-ion secondary battery for evaluation tests
each were nipped by chucks to be fixed, followed by being pulled in
opposite directions at a rate of 5 mm/min, and a maximum load until
fracture was measured to be designated as welding strength. A
distance between the chucks was 50 mm and the tab lead welding
portions were set so as to be disposed in the middle between the
chucks. A larger numerical value indicates a higher welding
strength. The result is shown in Table 1.
(Measurement of Internal Resistance)
[0124] An internal resistance of the lithium-ion secondary battery
for evaluation tests was measured at a measurement frequency of 1
kHz by an AC impedance method using an impedance meter (model
3532-80, produced by Hioki E.E. Corp.). A value under the condition
of an SOC (charge state) of 100% was designated as an internal
resistance value. An internal resistance value after battery
production is expressed as "Initial Value" and the result is shown
in Table 1.
(Cycle Test)
[0125] Using a charge and discharge device (produced by Toyo System
Co., Ltd.), the lithium-ion secondary battery for evaluation tests
was charged and discharged for 200 cycles at a current rate of 10
C. Thereafter, internal resistance was measured. The measurement
was made at a cut voltage of 2.7 to 4.2 V with an SOC of 100%. An
internal resistance value after 200-cycle charge and discharge is
expressed as "After 200 Cycles" and the result is shown in Table
1.
Example 2
[0126] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that the number of positive electrode
plates was changed to 30 and the number of negative electrode
palates was changed to 31, and then evaluated. The results are
shown in Table 1.
Example 3
[0127] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that the number of positive electrode
plates was changed to 50 and the number of negative electrode
palates was changed to 51, and then evaluated. The results are
shown in Table 1.
Example 4
[0128] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that the number of positive electrode
plates was changed to 80 and the number of negative electrode
palates was changed to 81, and then evaluated. The results are
shown in Table 1.
Example 5
[0129] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that an aluminum foil having the
thickness of 30 .mu.m was employed instead of the aluminum foil
having the thickness of 20 .mu.m, and then evaluated. The results
are shown in Table 1.
Example 6
[0130] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that an aluminum foil having the
thickness of 50 .mu.m was employed instead of the aluminum foil
having the thickness of 20 .mu.m, and then evaluated. The results
are shown in Table 1.
Example 7
[0131] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that a solid content concentration of
the undercoat layer coating liquid was adjusted and a coating
weight per unit area of one surface was changed to 1.2 g/m.sup.2,
and then evaluated. The results are shown in Table 1.
Example 8
[0132] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that a solid content concentration of
the undercoat layer coating liquid was adjusted and a coating
weight per unit area of one surface was changed to 2.7 g/m.sup.2,
and then evaluated. The results are shown in Table 1.
Example 9
[0133] A lithium-ion secondary battery was produced in the same
manner as in Example 2 except that in production of the positive
electrode plate, instead of the Al current collector, an aluminum
foil (A1N30 material) having a thickness of 20 .mu.m was used and
in production of the negative electrode plate, instead of the
electrolyte copper foil, a Cu current collector obtained by a
method to be described below was used, and then evaluated. The
results are shown in Table 1.
[0134] Tab lead welding strength was measured in the same manner as
in Example 2 except that instead of a portion welded with the
positive electrode tab lead, a portion welded with the negative
electrode tab lead was measured.
<Production of Cu Current Collector>
[0135] The undercoat layer coating liquid prepared in Example 1 was
applied entirely on one surface of an electrolyte copper foil
having a thickness of 10 .mu.m using a bar coating method.
Thereafter, heat treatment was carried out for 3 minutes at
180.degree. C. for drying. Then, The undercoat layer coating liquid
prepared in Example 1 was applied entirely on the the other surface
in the same manner to obtain a copper foil comprising an undercoat
layer formed on the both surfaces (hereinafter, occasionally
referred to as a Cu current collection member). A coating weight
per unit area of one surface of the undercoat layer was 0.5
g/m.sup.2. In measurement of the coating weight per unit area of
one surface, a small thin piece having a size of 100 mm.times.100
mm was accurately cut out from the Cu current collection member and
one surface of the small thin piece was treated with a remover
(trade name: NEOREVER#346, produced by Sansai Kako Co., Ltd.) and
the undercoat layer was removed from the one surface of the small
thin piece for calculation based on a mass difference before and
after the removal. A small thin piece having a size of 100
mm.times.100 mm was cut out from the Cu current collection member.
The small thin piece was used as a Cu current collector.
Example 10
[0136] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that in preparation of the undercoat
layer coating liquid, acetylene black was changed to graphite
(trade name; C-NERGY KS6L, produced by Timcal Ltd.), and then
evaluated. The results are shown in Table 1.
Example 11
[0137] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that in preparation of the undercoat
layer coating liquid, acetylene black was changed to carbon
nanotube (trade name: VGCF-H, produced by Showa Denko K.K.), and
then evaluated. The results are shown in Table 1.
Comparative Example 1
[0138] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that a solid content concentration of
the undercoat layer coating liquid was adjusted and a coating
weight per unit area of surface was changed to 4.8 g/m.sup.2, and
then evaluated. The results are shown in Table 1.
Comparative Example 2
[0139] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that a solid content concentration of
the undercoat layer coating liquid was adjusted and a coating
weight per unit area of surface was changed to 8.9 g/m.sup.2, and
then evaluated. The results are shown in Table 1.
Comparative Example 3
[0140] A lithium-ion secondary battery was produced in the same
manner as in Example 1 except that in production of the positive
electrode plate, instead of the Al current collector, an aluminum
foil (A1N30 material) having a thickness of 20 .mu.m was used, and
then evaluated.
[0141] The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Tab Lead Welding Portion Coating weight
Internal per unit Metal resistance Metal area of Foil (m.OMEGA.)
Metal Foil one Number of Total Welding After Electrode Foil
Thickness surface Electrode Thickness Strength Initial 200 Plate
Material (.mu.m) (g/m.sup.2) Plates (mm) (N) Value Cycles Ex. 1
Positive Al 20 0.5 15 0.3 121 1.7 1.7 Ex. 2 Positive Al 20 0.5 30
0.6 125 0.8 0.9 Ex. 3 Positive Al 20 0.5 50 1.0 108 0.5 0.5 Ex. 4
Positive Al 20 0.5 80 1.6 82 0.3 0.5 Ex. 5 Positive Al 30 0.5 15
0.45 101 1.8 2.0 Ex. 6 Positive Al 50 0.5 15 0.74 82 1.8 2.1 Ex. 7
Positive Al 20 1.2 15 0.3 111 1.7 2.1 Ex. 8 Positive Al 20 2.7 15
0.4 102 1.9 2.2 Ex. 9 Positive Cu 10 0.5 31 0.31 122 0.9 0.9 Ex. 10
Positive Al 20 0.5 15 0.3 97 1.7 1.8 Ex. 11 Positive Al 20 0.5 15
0.3 105 1.6 1.7 Comp. Positive Al 20 4.8 15 0.3 66 2.2 3.8 Ex. 1
Comp. Positive Al 20 8.9 15 0.3 54 5.0 9.9 Ex. 2 Comp. Positive Al
20 0 15 0.3 238 3.6 7.7 Ex. 3
Example 12
<Production of Electric Double Layer Capacitor>
[0142] There were mixed 100 parts by mass of activated carbon
(trade name: YP-50F, produced by Kuraray Chemical Co., Ltd.), 5
parts by mass of acetylene black (trade name: DENKA BLACK (powdery
article), produced by Denki Kagaku Kogyo K.K.), 7.5 parts by mass
of styrene butadiene rubber (trade name: NALSTAR SR-103, produced
by Nippon A&L Inc.), 2 parts by mass of carboxymethyl cellulose
(trade name: CMC DN-10L, produced by Daicel FineChem Ltd.), and 200
parts by mass of pure water to obtain a paste. The paste was
applied on both surfaces of the Al current collector using a doctor
blade method with the exception of a marginal portion of 10 mm
wide.times.100 mm long at one side of the Al current collector.
Thereafter, drying was carried out, followed by pressing to form an
electrode layer of 90 mm wide.times.100 mm long.times.80 .mu.m
thick on each of the both surfaces of the Al current collector. The
resulting product was used as an electrode plate for an electric
double layer capacitor. A marginal portion of 10 mm wide.times.100
mm long where the undercoat layer was exposed and no electrode
layer was formed was used as a tab lead welding portion.
[0143] Thirty-one electrode plates were prepared, and of these, 15
plates were used for a positive electrode and 16 plates were used
for a negative electrode. As illustrated in FIG. 9, these were
alternately stacked one by one, and a separator (trade name: TF40,
produced by Nippon Kodoshi Corp.) was inserted between the positive
electrode plate and the negative electrode plate to obtain an
electrode plate laminate in which the outermost layers of the
laminate were the negative electrode plate respectively.
[0144] Subsequently, two aluminum-made tab lead (made of A1N30-H, a
size of 0.5 mm thick.times.20 mm wide.times.30 mm long) were
prepared. One of the aluminum-made tab leads (positive electrode
tab lead) was welded to 15 tab lead welding portions of the
positive electrode plates in the electrode plate laminate using an
ultrasonic welder. The welding was carried out under conditions
involving a horn tip angle of 90 degrees, a pressure of 0.3 MPa, a
frequency of 20 kHz, and a duration of 0.3 seconds. The tip of the
horn had a rectangular shape of 2 mm.times.12 mm, and welding area
was 24 mm.sup.2.
[0145] The other aluminum-made tab lead (negative electrode tab
lead) was welded to 16 tab lead welding portions of the negative
electrode plates in the electrode plate laminate using an
ultrasonic welder. The welding was carried out under conditions
involving a horn tip angle of 90 degrees, a pressure of 0.3 MPa, a
frequency of 20 kHz, and a duration of 0.3 seconds. The tip of the
horn had a rectangular shape of 2 mm.times.12 mm, and welding area
was 24 mm.sup.2.
[0146] The thus-obtained electrode plate laminate was covered with
an aluminum laminated packaging material with the positive
electrode tab lead and the negative electrode tab lead each
protruded, and three sides were sealed to form a bag-like shape
having one side open. Moisture was eliminated using a vacuum dryer
set at 60.degree. C. Thereafter, an organic electrolyte solution
(trade name: LIPASTE-P/EAFIN (1 mole/1), produced by Toyama Pure
Chemical Industries, Ltd.) was poured in, followed by impregnation
for 24 hours in vacuum atmosphere. The opening of the aluminum
laminated packaging material was sealed using a vacuum sealer to
produce an electric double layer capacitor for evaluation
tests.
<Evaluation of Electric Double Layer Capacitor>
(Measurement of Welding Strength)
[0147] The measurement was carried out using a tabletop material
testing machine (STA-1150, produced by Orientech Co., Ltd.) in a
tensile test mode. The positive electrode tab lead and the
capacitor body part of the electric double layer capacitor for
evaluation tests each were nipped by chucks to be fixed, followed
by being pulled in opposite directions at a rate of 5 mm/min, and a
maximum load until fracture was measured to be designated as
welding strength. A distance between the chucks was set to be 50 mm
and the tab lead welding portions were set so as to be disposed in
the middle between the chucks. A larger numerical value indicates a
higher welding strength. The result is shown in Table 2.
(Measurement of Internal Resistance)
[0148] An internal resistance of the electric double layer
capacitor for evaluation tests was measured at a measurement
frequency of 1 kHz by an AC impedance method using an impedance
meter (model 3532-80, produced by Hioki E.E. Corp.). A value under
the condition of an SOC (charge state) of 100% was designated as an
internal resistance value. An internal resistance value after
capacitor production is expressed as "Initial Value" and the result
is shown in Table 2.
(Cycle Test)
[0149] Using a charge and discharge device (produced by Toyo System
Co., Ltd.), the electric double layer capacitor for evaluation
tests was charged and discharged for 500 cycles between 0 V and 2.5
V at a current density of 1.59 mA/cm.sup.2. Thereafter, internal
resistance was measured. An internal resistance value after
500-cycle charge and discharge is expressed as "After 500 Cycles"
and the result is shown in Table 2.
Example 13
[0150] An electric double layer capacitor was produced in the same
manner as in Example 12 except that a solid content concentration
of the undercoat layer coating liquid was adjusted and a coating
weight per unit area of surface was changed to 1.2 g/m.sup.2, and
then evaluated. The results are shown in Table 2.
Example 14
[0151] An electric double layer capacitor was produced in the same
manner as in Example 12 except that a solid content concentration
of the undercoat layer coating liquid was adjusted and a coating
weight per unit area of surface was changed to 2.7 g/m.sup.2, and
then evaluated. The results are shown in Table 2.
Comparative Example 4
[0152] An electric double layer capacitor was produced in the same
manner as in Example 12 except that a solid content concentration
of the undercoat layer coating liquid was adjusted and a coating
weight per unit area of surface was changed to 4.8 g/m.sup.2, and
then evaluated. The results are shown in Table 2.
Comparative Example 5
[0153] An electric double layer capacitor was produced in the same
manner as in Example 12 except that a solid content concentration
of the undercoat layer coating liquid was adjusted and a coating
weight per unit area of surface was changed to 8.9 g/m.sup.2, and
then evaluated. The results are shown in Table 2.
TABLE-US-00002 TABLE 2 Tab Lead Welding Portion Coating weight
Internal per unit Metal resistance Metal area of Foil (m.OMEGA.)
Metal Foil one Number of Total Welding After Electrode Foil
Thickness surface Electrode Thickness Strength Initial 500 Plate
Material (.mu.m) (g/m.sup.2) Plates (.mu.m) (N) Value Cycles Ex. 12
Positive Al 20 0.5 15 300 119 2.7 3.0 Ex. 13 Positive Al 20 1.2 15
300 110 2.8 3.0 Ex. 14 Positive Al 20 2.7 15 300 103 3.0 3.3 Comp.
Positive Al 20 4.8 15 300 69 3.6 9.8 Ex. 4 Comp. Positive Al 30 8.9
15 300 53 5.5 15.5 Ex. 5
EXPLANATION OF REFERENCE SIGNS
[0154] 1, 1': electrode plate [0155] 2, 2': metal foil [0156] 3,
3': undercoat layer [0157] 4, 4', 4'': active material layer [0158]
5n, 5n', 5n'': negative electrode tab lead [0159] 3n, 3n', 3n'':
tab lead welding portion of negative electrode [0160] 5p, 5p',
5p'': positive electrode tab lead [0161] 3p, 3p', 3p'': tab lead
welding portion of positive electrode [0162] S, S': separator
[0163] N, N', N'': Negative electrode [0164] P, P', P'': Positive
electrode
* * * * *